This invention relates to magnetically encoded data card security systems in which access at a secured location is controlled by a comparison of data on a card inserted by personnel into the system with data stored in the system and defining those persons who shall be granted access. More particularly, this invention relates to a system in which, in addition to the card data, keyboard data must be entered by persons wishing access, and wherein the keyboard data is a combination and permutation of the card data entered by persons wishing access.
Such systems, in the past, have utilized static magnetic card readers at remote locations for controlling access through electrically operable devices, such as doors, turnstiles, printers, etc. Prior art systems have been devised in which the remote card readers communicate with a central data processor or operate as stand-alone units.
The card or badge bearing encoded data used for controlling access is typically inserted in a slot of a reader which reads and decodes the data on the card. Advantageously, this data is encoded as a plurality of magnetically polarized spots in a strip of magnetic material. Such encoded data normally includes an identification number or numbers identifying the card holder. During use, this number encoded by the card is compared with a number or numbers stored in the central computer terminal or at the remote location to ascertain whether the individual inserting the card is entitled to access to a building, room, parking lot, or the like.
In one prior art embodiment, the magnetically polarized spots are used to directly actuate a reed relay or other moving switch mechanism located within the reader. The state of the art system is exemplified by U.S. Pat. No. 3,686,479 entitled Static Reader System For Magnetic Cards, assigned to A-T-O Inc., assignee of the present invention, employing electromagnetic solid state sensors disclosed and claimed in U.S. Pat. No. 3,717,749, also assigned to A-T-O Inc. These patents are hereby incorporated in this disclosure by reference. Such systems have been found to be very reliable and are in use as access control systems in a number of different industries, universities, and government installations.
Operation of such systems as a part of a security network employing a central processor is disclosed and claimed in U.S. Pat. No. 4,004,134, also assigned to A-T-O Inc. and also incorporated herein by reference. This latter system incorporates a central processor which periodically and sequentially polls each of the remote terminals in the system. The remote terminals are enabled to transfer data to the central processor only on receipt of a polling pulse. At the central terminal, data read at the remote location from an inserted card is compared with a master list which includes those persons who shall be given access at that remote location.
It has also been known in the prior art to include, at the remote location, a keyboard. Typically, such keyboard systems require that persons wishing access, in addition to the insertion of a magnetically encoded data card, are required to enter keyboard data, typically a sequence of digits. These digits have typically comprised a permutation and combination of the data encoded on the employee's card, the particular permutation and combination often being different for different remote terminals. In the past, however, the permutation and combination has generally been hard wired into the system, typically at the manufacturing plant, so that the system user was unable to alter the particular combination and permutation in the field after installation. Such a situation degraded the security of the overall system, since after a period of use, it was possible for persons to determine the particular order in which data must be entered in each keyboard in order to gain access into areas for which they are not authorized. In addition, as security problems or personnel turnover occurs in a particular facility, the prior art systems did not permit a change in the keyboard entry code required for authorization in order to reinstitute security in a location where security has been breached or is in jeopardy of being breached.